Quality analysis of included studies
| Selection | Comparability | Outcome | Total score (1–9) | |||||||
| (1) Representativeness of the exposed cohort | (2) Selection of the non-exposed cohort | (3) Ascertainment of exposure | (4) Demonstration that outcome of interest was not present at start of study | (1) Study controls for age, height, BMI, BP and gender (select the most important factor) | (2) Study controls for any additional factor | (1) Assessment of outcome | (2) Was follow-up long enough for outcomes to occur | (3) Adequacy of follow-up of cohorts | ||
| Kallio et al28 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 8 |
| Geerts et al27 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 8 |
| Yang et al29 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 3 |
| Ayer et al24 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 8 |
Note 1: 8–9 points stand for very good study quality; 6–7 points stand for good study quality; 4–5 points stand for satisfactory study quality; 0–3 points stand for unsatisfactory study quality.
Note 2: The Newcastle-Ottawa scale (online supplemental file A).
BMI, body mass index; BP, blood pressure.